Mechanical seals are devices primarily to seal rotating shafts turning relative to a housing, to protect the motor from the fluids be they slurry, suspension, or clear but corrosive, liquids immersing the impeller of a pump. As such, mechanical seals are often used in replacement of packing which is laid around the shaft in stuffing boxes. In general, the mechanical seal comprises a first element cylindrical in nature carrying on an axial face a generally circular sealing material, secured to the shaft to rotate therewith and a second element which is torodial in nature, secured to the housing wall and which carries, on an axial face opposite the first element axial sealing face a sealing material, generally coaxial with the shaft and in which the shaft turns freely. The seal defined by the opposed circular sealing materials is annular in configuration, and is defined by the interface of the engaged first and second parts. To accommodate progressive wear at the seal-forming interface, the rotating member is designed to be self-adjustable axially of the shaft. For this purpose, the first element comprises an inner and outer cylindrical member which are telescopically interfitted with a compression spring bias to progressively extend or elongate the first element of the seal assembly as the sealing materials wear, to maintain sealing engagement between the first and second elements.
Generally, the inner and outer members of the first element are keyed together for rotation with the shaft and at the same time guided in their axial relative movement by pins or tongues carried by one member which extend into mating structure in the opposite member. Thus, the inner and outer cylindrical members define an annular intermember space which may be filled with stiff or highly viscous fluid such as silicone grease as desired, e.g. through the axial face.